Production of solid carbon dioxide



June 22, 1937. MAlURl 2,084,403

I PRODUCTION OF SOLID CARBON DIOXIDE Original Filed Dec. 3, 1934fnlfemor: moo MFHURI HTTORNEY Patented June 22, 1937 accents PRODU nocannon pro on Guido Maiuri, dldwych, London, England, as-

signor to Mains-i Refrigeration Patents ted,

London, Eng

Original application camber 3, 1934, Serial No.

755,754. Divided and 1936, Se No. fiofl'il. in Great Britain .llc

lots This invention relates to the production of solid carbon dioxide,and its object is to cause carbon dioxide to freeze into dense blocks,the present application being a. division of my copending application,Serial No. 755,754, filed December 3, 1934.

It has already been proposed to produce dense blocks of solid carbondioxide by forming carbon dioxide snow by the expansion in a chamber ofliquid carbon dioxide, the snow being supported on a sieve beneath whichcarbon dioxide gas is drawn oil to cause liquid carbon dioxide topermeate and render the snow dense.

According to the present invention, liquid carbon dioxide at lowpressure is cooled to a solidifying temperature in a mould cooled by anevaporating refrigerating agent, whilst the liquid carbon dioxide issubjected to pressure conditions permitting evaporation therefrom. Thusthe low pressure liquid carbon diomde is subjected to the combinedcooling efiects of the evaporating refrigerating agent and ofevaporating carbon dioxide.

An installation for carrying out the invention is illustrated on theaccompanying drawing, which shows the installation in diagratlcsectional elevation.

a, is the boiler of an absorption refrigerating machine. b is thecondenser thereof, in which a. refrigerant such as ammonia is liquefiedand from which it is supplied by a pipe 0, having an expansion valve 0to the evaporator. in the present instance a coil 1: and jacketssurrounding a mould as will be described later. absorber of therefrigerating machine to which the evaporated refrigerant passes by apipe c. From the absorber d enriched absorption liquor is withdrawnalong a pipe I by a pump a, which delivers it to the boiler a by a; pipeM, a heat-exchanger 1, and a pipe h. Weak liquor is forced by the boilerpressure along a pipe 1 the heat-exchanger 1 and a. pipe 1 to thealtsorber d, past a pressure-reducing valve 1 k is a. mould surroundedby two superposed jackets l l constituting part of the evaporator of therefrigerating machine. Liquid refrigerant is supplied from the condenserb, by the pipe 0 and coil to the bottom of the upper it 1 The top of theupper jacket 1 is connected. 50 by a pipe m to the bottom of the lowerjacket 1 The top of the lower jacket F is connected disthe (ill. 52-121)single-stage compressor 0 to a pressure slightly above the triple pointpressure, for instance 7 atmospheres absolute.

The compressor 0 is driven by an tor p which also drives the pump a.

The compressed carbon dioxide gas passes by a pipe 41 to a cooler rwherein it is cooled to atmospheric temperature. From the cooler r thecompressed carbon dioxide passes by a pipe q to a heat-exchanger s, andthence by a pipe q into a series of jackets it. These jackets u jacketthe pipe coil 0 connected between the expansion valve 0 of the liquidammonia supply pipe 0 and the upper jacket I of the mould k. Thepressure conditions in the coil 0 are such electromm that the carbondioxide in the jackets u is subjected to a liquefying temperature andbecomes condensed therein. The liquid carbon dioxide drains by a pipe 10into a tank 20 wherein it is stored. The pipe 1) extends to near thebottom of the tank 10 so as to be sealed by the stored liquid carbondioxide. The top of the tank 10 is'vented by a pipe :1: into the jackets14..

Liquid carbon dioxide from the storage tank 20 is forced by the pressurealong a pipe 1/, having a stop cock 11 into the top of the mould is.

From the bottom of the mould k and beneath a perforated false bottom orpartition k permeable to gas but not to liquid, a pipe t leads to theheat-exchanger 3 which is connected by a pipe t to the gas supply pipe1: and consequently also to the suction of the compressor '0.

The sub-atmospheric pressure in the absorber d is arranged to be so lowthat the refrigerant in the jackets l l evaporates at temperatures suchas to maintain the internal surface of the mould at temperatures whichdecrease down-' wards from slightly above the triple point temperatureof carbon dioxide at the top to slightly below the triple pointtemperature of carbon dioxide at the bottom. These differences oftemjacket 1 evaporating against the static pressure head of the liquidrefrigerant in the lower jacket P.

Owing to the temperatures reigning in the.

mould k, the liquid carbon dioxide entering the mould k by the pipe 2flows down the mould and solidifies on the perforated false bottom It,the apertures of which are covered with gauze impermeable, owing tosurface tension, by liquid no.1 dioxide although permeable to gaseous wdioxide. At the same time the suction an. by the compressor 0 on thespace beneath the false bottom k of the mould causes some of the carbondioxide to evaporate and thereby exert an additional cooling eflect onthe remainder within the mould.

The reduced pressure beneath the false bottom k not only will induceevaporation of some of the carbon dioxide and so assist in freezing theremainder, but will also draw liquid carbon dioxide into any intersticesin the block of solid carbon dioxide to freeze therein, thus promotingcontinuity of the dense structure of the block.

The mould is is partially filled with liquid carbon dioxide from thetank 10, and, after closing the stop cock y in the pipe 11 which leadsfrom the bottom of the tank, the mould is placed in communication withthe top of the tank w by opening a stop cock y in a pipe 1/interconnecting the upper portions of the tank and mould. The gaseouscarbon dioxide thus admitted to the mould liquefies and fillsinterstices in the solid carbon dioxide due to shrinkage of theliquefied carbon dioxide on solidifying.

The block of carbon dioxide ice is removed from the mould k on removinga bottom cover It and the false bottom Id.

The freezing of carbon dioxide by the evaporation of the refrigerantaccompanied by expansion of some of the liquid carbon dioxide, is moreeconomical in carbon dioxide and in motive power for re-compressionthereof than the known method of internal cooling by expansion of liquidcarbon dioxide and utilizing for external cooling the sensible cold ofthe produced carbon dioxide gas, for in the former case the evaporatingaoeaacs refrigerant exerts an energetic cooling effect equal to of thetotal of that required, whereas in the latter case the external coolinghardly compensates for the inward leakage of heat through the usual heatinsulation.

I claim:

l. A method of producing dense solid carbon dioxide in a mould,consisting in cooling the upper portion of said mould to a. temperatureslightly above and the lower portion of said mould to a temperaturebelow the triple point temperature of carbon dioxide, partially fillingsaid mould with'liquid carbon dioxide, applying suction to the undersurface of said carbon dioxide in said mould, and admitting gaseouscarbon dioxide at slightly above the triple point pressure oI carbondioxide into said-mould above said liquid carbon dioxide until saidliquid carbon dioxide in said mold is frozen. v

2. A method of producing dense solid carbon dioxide in a mould,consisting in cooling said mould by evaporating a liquid refrigerantunder a plurality of slightly different pressures causing thetemperatures of said mould to decrease downwards from slightly above tobelow the triple point temperature of carbon dioxide, paroxide, applyingsuction to the under surface of said carbon dioxide in said mould, andadmitting gaseous carbon dioxide at slightly above the triple pointpressure of carbon dioxide into said mould above said liquid carbondioxide until said liquid carbon dioxide in said mould is frozen.

GUIDOMAI RI.

tially filling said mould with liquid carbon dl-

